As technology advances and the processing capabilities of digital computing devices increases, higher bandwidth networks are needed to interconnect the computing devices and facilitate use of the increasing computing power. However increasing network data rates can be problematic due to limited channel bandwidth. The bandwidth of an electrical channel (e.g., a transmission line) may be reduced by physical effects, such as skin effect, dielectric loss, and reflections due to impedance discontinuities.
Limited channel bandwidth can cause a transmitted pulse to spread across more than one unit interval, and as a result, the received signal may suffer from inter-symbol interference. Equalization functions may be added the input and/or output circuitry of a network to compensate for signal distortions resulting from limited channel.
A decision feedback equalizer (DFE) is a nonlinear equalizer that is well suited to equalizing a high-loss channel. Unlike linear equalizers, the DFE is able to flatten channel response and reduce signal distortion without amplifying noise or crosstalk, which is an important advantage when equalizing a high loss channel.
In a DFE, previously received bits are weighted, fed back, and added to the received input signal. If the magnitudes and polarities of the weights applied to the previously received bits are properly adjusted to match the channel characteristics, the inter-symbol interference from the previous bits in the data stream will be cancelled, and the bits can be detected with a low bit error rate.